Patellar Luxation
Patellar luxation is the dislocation of the patella (kneecap). The condition can result from trauma that caused the knee to be forced out of normal alignment, but is more often genetic in nature.
The patella may dislocate toward the inside (medial) or outside (lateral) of the leg. It can affect either or both legs. The most common occurrence of luxating patella is the medial presentation in small or miniature dog breeds.
Signs of luxation may appear as early as weaning or may go undetected until later in life. Signs include intermittent rear leg lameness, often shifting from one leg to the other, and an inability to fully extend the stifle. Early in the course of the disease, or in mildly affected animals, a hopping or skipping action occurs. This is due to the patella luxating while the dog is moving and by giving an extra hop or skip the dog extends its stifle and is often able to replace the patella until the next luxation, when the cycle repeats.
There are several degrees of luxation, with the lower grade being the ability of the kneecap to pop back into place on its own and the highest grade (of four) being such severe luxation that only surgical repair can correct the dislocation.
A veterinary examination can determine if the knee structure is stable. Breeders should have breeding stock screened to check for patellar luxation. Evaluations done after the dog is 12 months old may be submitted to OFA and unaffected dogs will be issued an OFA number. Currently most TT breeders testing for patellar luxation are not taking this extra step, so OFA does not publish any statistics on the frequency of the condition in the breed.